Mechanism of the ORR. AbstractThe mechanism of the oxygen reduction reaction (ORR) on polyimide-based N-doped carbon catalysts with and without Fe (i.e., Fe-N-C and N-C) in acidic media was studied, using a rotating ring-disk electrode voltammetry, based on the estimation of the rate constants of the

The ORR activity and durability of Fe-containing non-precious N-doped carbon catalysts in acidic medium were studied using a rotating ring-disk electrode voltammetry and XPS technique.

Urea-functionalized 4-ethynylbenzenes undergo facile formal [2 + 2] cycloaddition followed by retroelectrocyclization upon reaction with tetracyanoethylene, yielding 1,1,4,4-tetracyanobuta-1,3-dienes-based push–pull chromophores. Unlike the N,N′-dialkylamino group, urea functionalization provides easy access to further functionalization on these chromophores. The resulting chromophores exhibit unexpected white light emissions apart from various inherent properties like intramolecular charge-transfer band and redox behavior.

Understanding the kinetics of the oxygen reduction reaction (ORR) for fuel cell applications is quite important but difficult because the four-electron pathway is often overestimated by including a quasi-four-electron pathway that consists of the formation and reduction of H2O2. To solve this problem, here we demonstrate a novel analysis method with experimental data over a Pt-free Fe/N/C cathode catalyst. In this study, H2O2 voltammetry was conducted separately to evaluate the rate constant of the H2O2 reduction more accurately, and the obtained data were combinatorally analyzed with those from the ORR experiments. First, mathematical modification of the conventional Damjanovic approach was performed, and then the effect of the catalyst loading density was carefully studied by utilizing a novel reaction model with consideration of the quasi-four-electron pathway to avoid overestimation of the four-electron pathway kinetic parameters. In the most overestimated case, the percentages contribution of four-electron pathway over the Fe/N/C catalyst was estimated as 85% with the conventional Damjanovic model, while that from the newly proposed model is 51%. This method will be applicable for many other cathode catalysts and will facilitate understanding the nature of the ORR.

Nitrogen-doped carbon catalysts for the electrochemical oxygen reduction reaction (ORR) have great potential to substitute precious metal alloy catalysts for the electrochemical synthesis of H 2 O 2 based on a fuel cell setup. Consequently, obtaining a kinetic understanding of nitrogen-doped carbon catalysts in acidic media is essential. In this study, the mathematically modified Damjanovic model and Nabae model were applied to calculate the kinetic constants for an N/C catalyst prepared from polyimide particles. The results show that the N/C catalyst has high selectivity for the two-electron reduction of O 2 , making it a promising catalyst for the electrochemical production of H 2 O 2 . This study gives quantitative insight into the oxygen reduction reaction mechanism over an N/C catalyst prepared by the pyrolysis of polyimide nanoparticles.

A simple color change detection by the naked-eye using untreated paper for a biologically relevant fluoride (F -) anion in water is a challenge. New non-planar push-pull chromophore involving intramolecular charge-transfer (ICT) from urea donor in 2,3disubstituted-1,1,4,4-tetracyanobuta-1,3-diene (TCBD) turns out to be an efficient system for detecting Fion giving various output signals. But, replacing phenyl (Ph) at C3-position with 4-(dimethylamino)phenyl (DMA) led to the absence of colorimetric and fluorometric detections due to the masking and quenching, nature of strong ICT by the DMA. NMR and electrochemical studies revealed that the sensing mechanism is governed by H-bonding as well as the deprotonation of N-H attached with TCBD moiety which reduces the HOMO-LUMO gap and causes the dramatic color change. Coupled with excellent sensitivity (3 ppm) and specificity towards F -, a successful demonstration of cheap tissue paper-based visual stripdetection in aqueous is presented.

Supporting InformationThe relaxed scan potential energy diagram and the electrostatic potential mapping of the neutral and the anionic radical of the dichlorobiphenyls are given in the Supporting

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